Graphite particles have various excellent characteristics such as excellent heat resistance, chemical resistance, mechanical strength, thermal conductivity, and electrical conductivity, as well as lubricity and light weight. In various fields, the characteristics of graphite particles are imparted to resin-formed articles and the like by dispersing graphite particles in a resin. However, graphite particles are easily aggregated, have a low affinity for resins or solvents, and hence are dispersed in a resin or a solvent in an aggregated state. When graphite particles in such an aggregated state are dispersed in a resin or a solvent, the characteristics tend to be expressed insufficiently.
For this reason, various methods for preparing fine graphite particles have been proposed so far in order to highly disperse graphite particles in a resin or a solvent. For example, Japanese Unexamined Patent Application Publication No. Hei 2-204317 (PTL 1) discloses a method for preparing a fine graphite by dry-grinding a graphite powder with a vibration mill. Although graphite particles become fine, such a mechanical process has a problem that the structure of the graphite is destroyed, and hence the electrical conductivity, thermal conductivity, and mechanical strength of the obtained fine graphite particles are lowered.
Japanese Unexamined Patent Application Publication No. 2005-53773 (PTL 2) discloses a method for preparing thin film-shaped graphite oxide particles by oxidizing graphite. Moreover, Japanese Unexamined Patent Application Publication No. 2009-242209 (PTL 3) discloses a method for organically modifying a graphite by ion-exchange a cation on a surface of a surface-oxidized graphite obtained by subjecting the graphite to an oxidation treatment for a cationic organic compound. According to these methods, graphite oxide particles can be obtained which can be highly dispersed in a resin or a solvent, and the characteristics of graphite can be imparted to a resin or the like by dispersing such graphite oxide particles in the resin.
However, the characteristics of fine graphite particles obtained by oxidation tend to be degraded as compared with the characteristics of the graphite particles used as the raw material, and such fine graphite particles still have room for improvement in terms of sufficient expression of original characteristics of graphite.